1. Field of the Invention
The present invention relates to a built-in type antenna apparatus for a portable terminal, and more particularly to a built-in type antenna apparatus for a portable terminal which separates an antenna from a slot antenna and includes an additional sub-antenna.
2. Description of the Related Art
Generally, portable communication devices refer to small and mobile devices by which radio communication can be performed. The Portable communication devices include a hand held phone (HHP), CT-2 cellular phone, a digital phone, a Personal communication system (PCS) phone, and a Personal digital assistant (PDA), and are classified according to their shapes. For example, the terminals are classified into a bar type, a flip type, a folding type, and a sliding type according to their shapes. The above-mentioned portable terminals inevitably include an antenna apparatus, a data input and output device, and a data transceiver. The data output device is generally an LCD.
Basically, a plurality of keys are arranged on a key pad used for data input. The keys include a send (SND) key which is a communication start button, a cancel key, a clear key (CLR), number keys, letter keys, an end (END) key, function keys, a power (PWR) key, etc.
Recently, the number of subscribers of the portable terminals has dramatically increased, and the portable terminals are so generalized that almost everyone carries a portable terminal. Although the portable terminals simply provided voice services at the beginning, portable terminals providing an AM/FM radio, MP3, moving image display, remote control, and other functions are now on the market.
Further, portable terminals providing a camera function and a high speed data communication function as well as a voice communication function have been developed. This means that many devices for satisfying various desires of consumers are installed in the portable terminals, and space for built-in antennas become smaller as the mounting areas of the other parts become larger.
The antennas are usually whip or helical antennas. The helical antenna is generally used to lower the mounting height of the antenna. Different from a rod antenna in which a rod is drawn to extend the length of the antenna, the helical antenna has a protruding portion on one side of the upper portion of the body of the terminal and is detachably fixed to the terminal. However, a terminal having a helical antenna does not have a good appearance due to the protruding portion of the antenna.
Built-in type antennas have become widely used in the terminals to resolve the above-mentioned disadvantage. A chip antenna, a planar inverted F antenna (PIFA), and a built in micro-strip patch antenna are mainly used as the built-in type antenna.
As shown in FIGS. 1 to 3, according to a built-in type antenna 3, a dielectric body and a conductive body (not shown) are installed at the upper end portion of a printed circuit board (PCB) 2 provided in a terminal 1, separated by an antenna installing portion 4. Transmission and reception of waves are satisfactorily performed only if the installing portion 4 provides the printed circuit board 2 with a predetermined height. Therefore, the built-in type antenna 3 is designed such that it is separated from the printed circuit board 2 by a predetermined height.
However, the conventional built-in type antenna has been mainly used in folding type and sliding type terminals. Since the folding type or sliding type terminal has a structure in which cases of the terminal are closed in a state in which they face each other, the antenna mounted into the body of the terminal performs the functions of a built-in type antenna in a state in which the terminal is opened, but the built-in antenna may be screened due to metal parts (e.g. a metal cover of an LCD and other metal parts) provided in the terminal before the terminal is opened. Then, the terminal is in a reception waiting state which shows a low reception rate. Further, as the thickness of the terminal becomes reduced, the mounting space of the built-in type antenna is also reduced and therefore the height of the antenna is lowered and an additional efficiency drop is generated. Therefore, an inclination property and a gain of the built-in type antenna are not sufficiently secured. Further, it becomes difficult to secure the performance and the radiation efficiency of the terminal.